Compositions containing organopolysiloxanes and metal hydroxides or hydrates of metal oxides such as cerium hydroxide or aluminum hydrate which form curable flame-retardant or self-extinguishing elastomers are known in the art. For example, U.S. Pat. No. 3,821,140 to Milbert discloses an organopolysiloxane composition which is curable to a fire-resistant elastomer comprising (a) an organopolysiloxane rubber in which at least 50 percent of the organic radicals are methyl radicals, (b) an inorganic filler, (c) an organic peroxide, (d) from 0.001 to 0.01 parts of an additive comprising platinum and (e) either 3 to 35 parts of a rare earth metal oxide, or 1 to 8 parts of a rare earth metal hydroxide, per 100 parts of the organopolysiloxane rubber.
Also, U.S. Pat. No. 3,677,999 to Denk et al discloses a cast resin molding material base of epoxide polyester, phenol, polyurethane and silicone cast resin masses containing aluminum oxide trihydrate and a fine structured silica fossil.
In contrast to the flame-retardant and self-extinguishing elastomers described above, the compositions of this invention provide elastomers having better flame-retardant and self-extinguishing properties than the elastomers known heretofore. Furthermore, the elastomers obtained from the room temperature curable compositions of this invention exhibit higher tensile strength and better resistance to tear propagation than elastomers obtained from previously known compositions.
Therefore, it is an object of this invention to provide elastomers having improved flame-retardant and self-extinguishing properties. Another object of this invention is to provide flame-retardant elastomers having improved tensile strength. A further object of this invention is to provide flame-retardant room temperature elastomers having improved tensile strength and improved resistance to tear propagation.